Various models for faults in transmission lines and their detection using time domain reflectometry

Abstract

This paper presents new ways of modelling several types of faults that can be encountered while monitoring cables throughout their lifecycle. These models comply with the traditional RLGC representation of a transmission line, which makes them easily usable for numerical simulations in frequency-domain. Theoretical fault signatures will then be extracted in time-domain to provide a better way of analyzing plots given by traditional devices, like time domain reflectometers (TDR). This allows a more accurate assessment of a cable’s health and condition. It will be shown in particular that some faults can be detected even if their damaged zone remains small compared to the wavelength. A direct benefit from this is that very expensive high frequency tools are not always necessary to detect these faults. The general objective of this paper is to improve fault location accuracy by combining measurement and simulation. It will be shown how this combination can become a powerful tool to detect, locate, and characterize a defect in a cable. The suggested models can be applied to any type of cable, from a coaxial line to a multi wire harness. In this work, a focus has been put on civil and military aircrafts, but similar cables are also found in cars or nuclear power plants for instance.